The present invention relates generally to electric rocker switches, and more particularly, to switches including a gull wing shaped rocking contact having upper actuating surfaces and lower centering and pivoting surfaces.
Rocker actuated electrical switches are well known in the art and numerous designs thereof may be found in commerce. For example, as shown in FIG. 1, a switch 10 is disclosed in U.S. Pat. No. 4,203,017. The switch 10 comprises a rocking actuator 12 pivotally mounted on a pivot 14. A spring follower guide 18 is molded integrally with the rocking actuator 12 and extends downwardly therefrom. The spring follower 20 is reciprocally mounted in a cylindrical bore 22 in the spring follower guide 18, and a compression spring 24 is compressed between the top 26 of the bore and the bottom 28 of a counterbore 30 in the spring follower 20.
The compression spring 24 biases the spring follower 20 downwardly, in a direction to eject it from the spring follower bore 22 were it not restrained from such ejection. The spring follower 20 has a blunt point end portion 50 that presses against a rounded V-shaped portion 52 of a rocking contact 54. The V-shaped portion 52 is formed by a curved central part of a rocking contact 54 lying between and joining two upstanding, diverging portions 56, 58 of the rocking contact 54. Beyond the diverging portions, the rocking contact 54 bends downward, then outward at its respective ends to form contacts 74, 76. The contacts 74, 76 match respectively with side terminals 70, 72. The contacts 74, 76 and side terminals 70, 72 collectively form circuit making and breaking surfaces.
A known problem with such rocker switches 10 is the tendency of the rocking contact 54 to lose its centered rest position with respect to its supporting elements. There is a tendency for the rocking contact 54 to slide laterally or rotate angularly with respect to its support as it tilts from side to side. This adversely affects the ability of the contacts 74, 76 to make a clean break with the side terminals 70, 72. This sliding action can ultimately lead to switch failure by allowing the V-shaped portion 52 to come to rest away from its centered position, preventing one of the contacts 74, 76 from adequately breaking contact with its respective side terminal 70, 72.
To prevent this off-center sliding of the rocking contact 54, prior art devices have used various supporting and pivoting elements. As shown in FIG. 2, the rocking contact 54 has an integral rectangular conductive bearing plate 80 that rests in rectangular notches 82, 84 in the top edges of a pair of spaced apart parallel side walls 86, 88 of a center terminal 78. Ideally, the placement of the rectangular plate 80 in the notches 82, 84 limits the lateral movement of the rocking contact 54. However, lateral movement is only limited if the plate fits precisely within the notches 82, 84. This prerequisite requires a high degree of manufacturing accuracy. Accordingly, the tolerance for manufacturing flaws is low. If there are imperfections, as is common in the course of manufacturing, the rocking contact will still be able to shift laterally.
Additionally, the use of the rectangular plate 80 does not restrain the axis of angular rotation of the rocking contact 54 during switch operation. Although the plate 80 prevents lateral movement, the rocking contact 54 can still rotate and translate such that its axis of angular orientation is off-center. Depending on the severity of this movement, the problem can cause the switch 10 to fail by biasing the switch 10 in the direction of one of the two contacts 74, 76. This affects the ability of the rocking contact 54 to make a clean break with the side terminal 72, 74 toward which it is biased. This may also affect the ability of the other contact to reach the side terminal 72, 74 on the opposite side. Accordingly, it is desirable to minimize both the lateral movement of the rocking contact 54 and movement of the axis of angular rotation and during the operation of the rocker switch 10.
Another disadvantage of known rocker switches is that, generally, the rotation angle of the rocking actuator 12 is in the range of 15 to 30 degrees. In modern applications, it is often ergonomically desirable to limit the angle of actuator rotation to under 10 degrees, and preferably, as low as 7 degrees. The problem with limiting the rotation angle of the rocking actuator 12 is that the motion of the spring follower 18 is likewise limited. If the spring follower 18 does not move sufficiently up the diverging portions 56, 58 of the rocking contact 54, it will not be able to exert enough force to cause one of the contacts 74, 76 to reach its respective side terminal 70, 72. Accordingly, it is desirable to limit the angle of the rocking actuator rotation while ensuring that sufficient force will be applied by the follower to enable the contact elements to make contact with the side terminals 70, 72.
There is, therefore, a need for a rocker switch in which the rocking contact and its supporting elements insure a reliable return of the contact to a centered rest position and which may be operated with a relatively low rotation angle of the rocking actuator. Therefore, it is an objective of the present invention to provide for a rocker switch that improves upon conventional designs.
To accomplish the above and other objectives, the present invention provides for an improved electric rocker switch. In a presently preferred embodiment, the present invention provides for an electric rocker switch having a gull wing shaped rocking contact. The rocking contact pivots on a pair of upright blades of a center terminal. At least one centering protrusion disposed on a portion of a lower surface of the rocking contact rests between the upright blades when the rocking contact is in a centered position, which prevents lateral movement of the rocking contact beyond limits of the upright blades. First and second rocker contacts are located on opposite sides of the rocking contact. The first and second rocker contacts face first and second fixed contacts, respectively, such that the first rocker contact touches the first fixed contact when the rocking contact rocks to one side, and the second rocker contact touches the second fixed contact when the rocking contact rocks to the other side. Positioning surfaces are disposed on the lower surface of the rocking contact adjacent to the centering protrusion. The positioning surfaces and top inside edges of the upright blades serve as pivots for the rocking contact as it tilts from side to side.
Other features and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein this and other presently preferred embodiments of the invention are shown and described by way of illustration of the best mode completed of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly the drawings and description are to be regarded as illustrative in nature and not as restrictive.